After initially declining to sign up, technology giant Google has joined a growing number of companies committing to a “student privacy pledge” created by advocacy groups and endorsed by the White House.

Google has come under heavy scrutiny for privacy practices that critics have feared would open the door to students’ personal information being used for advertising purposes, and the company has revised its policies in the face of those questions.

The privacy pledge is being sponsored by the Future of Privacy Forum, a Washington-based think tank that advocates for responsible data use, and the Software & Information Industry Association, a leading trade association, also headquartered in the nation’s capital.

At the time of the president’s announcement, the pledge had been signed by 75 companies—though Google, among others, was noticeably absent from the list. As of today, the number of signatories had risen to 91.

“Protecting the privacy and security of all of our users, including students, is a top priority,” the company said in a statement. “We’re pleased to see the ed-tech industry come together to support this important issue and we’ve signed the pledge to reaffirm the commitments we’ve made directly to our customers.”

Any possibility that the pledge might have slipped from the public’s attention vanished last week, when President Barack Obama publicly lauded the effort and urged more companies to get on board.

The president also said that if companies didn’t get sign up, “we intend to make sure that those parents and those schools know that you haven’t joined.”

Jules Polonetsky, the executive director of the Future of Privacy Forum, declined to comment on Google joining the list of signatories, which he said occurred late last week, or on any other specific company’s pledge. But he said there was clear momentum among both young and established tech companies to meet the standards set in the document.

“Sometimes, it takes a while for these things to snowball,” Polonetsky said in an interview. But after the president’s speech, “we saw an uptick right away.”

Polonetsky has worked in both the public and private sector on privacy issues. He served as chief privacy officer at AOL, as a state lawmaker in New York, and as New York City’s consumer affairs commissioner. He said some of the pressure on companies to agree to the pledge had risen from parents, who have asked K-12 officials and vendors why companies contracting with districts hadn’t met the standard.

“A good contract with a vendor should already include those practices,” Polonetsky said, “but this puts them on the hook.”

By signing the pledge, companies agree to hold the line on data privacy several fronts, including not selling student information, not using online behavior to target advertising, using data for “authorized education purposes” only, agreeing to strict limits on retaining data, and giving parents access to information collected about their children.

Companies also agree to “not build a personal profile of a student other than for supporting authorized educational/school purposes or as authorized by the parent/student.”

Mark Schneiderman, the senior director of education policy for the SIIA, said that since the pledge was announced in October, about 25 additional companies per month were signing up. The organizers of the pledge want to make sure that vendors understand their commitment, before they agree to take part.

“When the President speaks it creates a lot of attention,” Schneiderman said, calling it “great marketing” for the effort.

Sean Cavanagh is Senior Editor of EdWeek Market Brief. He is also a reporter and editor for Education Week, where he has covered a variety of beats since 2002. His primary focus is on business and technology issues in K-12 education. Previously he covered math and science education, charter schools and school choice, and federal policy. Before joining Education Week, he was a reporter for daily newspapers in Tennessee and Florida.